Recently, various types of power retailers are present. For example in Japan, after a monopoly by a general electric company a long time ago, enforcement of the Revised Electric Business Act has paved the way for partial liberalization of power retailing.
For example, specific scale electric companies (Power Producers and Suppliers: PPS) are permitted to sell power to a heavy consumer whose contract demand is 50 kW or more. The heavy consumer is able to enjoy the merit of reducing the cost of power by selecting an electric company which offers a contract on advantageous terms. In connection with the specific scale electric companies, various techniques targeted for cost reduction have been proposed. (For example, refer to Patent Literature 1.)
FIG. 12 is a conceptual view of power supply from a specific scale electric company to a consumer. A specific scale electric company 220 receives power supply from a power supplier 210. The power supplier herein refers to a company, such as a general electric company, who has a power generation facility.
The specific scale electric company 220 supplies, by way of a transmission and distribution network 230, the power received from the power supplier 210 to a consumer 240 with whom a contract has been made. The transmission and distribution 230 is normally managed by the general electric company.
Because of the need to prepare a power generation plan by estimating the amount of power generation required, the power supplier 210 requests notification in advance, from the specific scale electric company 220, of an estimated value of a power demand for a single day in the unit of, for example, 30 minutes.
When the amount of power (the power demand) that the specific scale electric company 220 is actually supplied from the power supplier 210 is close to (e.g., within ±3% of) the estimated power demand, the specific scale electric company 220 may purchase the power from the power supplier 210 at low cost (i.e., keep imbalance charges relatively low). On the other hand, when, for example, the power demand exceeds the estimated power demand by 3% or more, the power supplier 210 imposes a higher power retail price as a penalty, and the specific scale electric company 220 incurs expensive imbalance charges for the amount of power exceeding the estimated power demand.
Meanwhile, when the power demand is less than the estimated power demand and a surplus occurs, if the surplus is within 3% of the estimated power demand, the power supplier 210 purchases the surplus at a certain level of price. However, if the surplus is as much as 3% or more of the estimated power demand, the power supplier 210 collects the surplus without any purchase price settings. That is to say, the surplus is collected for free. Accordingly, it is preferable for the specific scale electric company 220 not only to simply reduce the power demand but to approximate the power demand to the estimated power demand.
The reason why the power supplier 210 sets relatively low imbalance charges for the cases when the power demand is close to the estimated power demand is that the power supplier 210 may also enjoy merits, such as facilitation of preparation of the power generation plan. Thus, the more the specific scale electric company 220 succeeds in operating at the power demand within a range close to the estimated power demand, the more credibility the estimated value will have, and this in turn allows the power supplier 210 to prepare the power generation plan with a higher precision. Accordingly, by succeeding in operating at the power demand within a range close to the estimated power demand, the specific scale electric company 220 may also reduce the imbalance charges due to the power supplier 210.